Is there any sort of timetable for that, even a rough one? Are PC gamers looking at a year-long wait here?

We unfortunately do not have a timetable for this project yet. Truth be told, every single Bungie employee and his brother worked their butts off to get Halo Xbox completed and they are all on a much deserved vacation right now. When they all get back and their sunburns finally stop hurting they will tackle Halo for any and all other platforms.